Recent work in this laboratory has shown that a variety of cancer cells secrete nerve growth factor. In particular, mouse L-cells secrete large quantities of the factor in culture. Further, the chemical properties of L-cell NGF are different from any form of NGF which has so far been studied. We now propose: 1) to grow large quantities of L-cells; 2) to isolate and to completely purify the NGF secreted by these cells; 3) to determine the molecular properties and structure of this protein; 4) to ascertain whether this naturally occurring form of NGF has biologic actions which have heretofore not been recognized, both within the nervous system as well as outside of it. We further propose to completely purify human nerve growth factor from serum, to characterize it chemically, and to develop specific immunoassays for it. Such assays will then permit the specific measurement of NGF in man.